Comparison of SARS-CoV-2 Reverse Transcriptase Polymerase Chain Reaction and BinaxNOW Rapid Antigen Tests at a Community Site During an Omicron Surge
Authors: Tobias Todsen, Thomas Benfield
Journal: Annals of Internal Medicine (2022)

LettersOctober 2022Comparison of SARS-CoV-2 Reverse Transcriptase Polymerase Chain Reaction and BinaxNOW Rapid Antigen Tests at a Community Site During an Omicron SurgeFREETobias Todsen, MD, PhD and Thomas Benfield, MD, DMSciTobias Todsen, MD, PhDRigshospitalet and Copenhagen Academy for Medical Education and Simulation, Copenhagen, Denmark and Thomas Benfield, MD, DMSciAmager and Hvidovre Hospital, Hvidovre, DenmarkAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/L22-0256 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail TO THE EDITOR: We congratulate Schrom and colleagues (1) on their important study on the diagnostic performance of rapid antigen and molecular testing of different sampling specimens for SARS-CoV-2. However, we question their conclusion that throat swabs (also called oropharyngeal swabs) are inferior to anterior nasal swabs.The authors state that "throat (tonsillar) swabs" were collected from a subgroup of participants in the study but do not report further on the swab type (that is, the material and design) and sample technique. It is therefore unclear whether the posterior oropharyngeal wall—considered the essential specimen collection site for throat swabs—was also sampled in this study, as recommended by the Centers for Disease Control and Prevention (2). If no specimen from this site was included in the sample, it should be defined as a "tonsillar swab" instead of a "throat swab."Details on how the investigators trained the laboratory assistants in collecting throat swabs before the study are also needed. Collecting throat swabs requires special anatomical knowledge and clinical skills to visualize and swab the posterior oropharyngeal wall without touching the tongue and cheek. Therefore, the Centers for Disease Control and Prevention recommends that only trained health care providers should collect throat swabs in order to avoid false-negative results. Although the laboratory assistants in Schrom and colleagues' study were certified and experienced in collecting nasal swabs, their experience with throat swabs may have been limited. As they collected all the throat swabs during a single day, many of these may have been obtained at the initial stage of a learning curve (3).Finally, whether the laboratory assistant collected 1 swab for antigen testing and a new swab for molecular testing is unclear. Furthermore, were the throat swabs subsequently collected after the 2 nasal swabs, or was the order randomized? If the laboratory assistants collected throat swabs last, the sample quality might decrease because of participant discomfort during the third and fourth swabs.The sensitivity of throat swabs for SARS-CoV-2 using molecular testing is much lower in Schrom and colleagues' study (58/96 [60%]) than in a systematic review that reported a difference in sensitivity of 12 percentage points for throat swabs compared with nasal swabs (4). The greater sensitivity of throat swabs reported in previous studies may indicate that the laboratory assistants in Schrom and colleagues' study performed a suboptimal throat sample procedure. However, direct comparison is difficult because specimen collection descriptions are missing; these should be reported according to the Standards for Reporting of Diagnostic Accuracy guidelines (5).References1. Schrom J, Marquez C, Pilarowski G, et al. Comparison of SARS-CoV-2 reverse transcriptase polymerase chain reaction and BinaxNOW rapid antigen tests at a community site during an Omicron surge. A cross-sectional study. Ann Intern Med. 2022;175:682-90. [PMID: 35286144] doi:10.7326/M22-0202 LinkGoogle Scholar2. Centers for Disease Control and Prevention. Interim Guidelines for Collecting and Handling of Clinical Specimens for COVID-19 Testing. 2022. Accessed at www.cdc.gov/coronavirus/2019-ncov/lab/guidelines-clinical-specimens.html on 6 June 2022. Google Scholar3. Todsen T, Bohr A, Hovgaard LH, et al. Valid and reliable assessment of upper respiratory tract specimen collection skills during the COVID-19 pandemic. Diagnostics (Basel). 2021;11. [PMID: 34829333] doi:10.3390/diagnostics11111987 CrossrefMedlineGoogle Scholar4. Tsang NNY, So HC, Ip DKM. Is oropharyngeal sampling a reliable test to detect SARS-CoV-2? Authors' reply [Letter]. Lancet Infect Dis. 2021;21:1348-9. [PMID: 34363770] doi:10.1016/S1473-3099(21)00402-3 CrossrefMedlineGoogle Scholar5. Bossuyt PM, Reitsma JB, Bruns DE, et al; Standards for Reporting of Diagnostic Accuracy. Towards complete and accurate reporting of studies of diagnostic accuracy: the STARD Initiative. Ann Intern Med. 2003;138:40-4. [PMID: 12513043] LinkGoogle Scholar Comments0 CommentsSign In to Submit A Comment Author, Article, and Disclosure InformationAuthors: Tobias Todsen, MD, PhD; Thomas Benfield, MD, DMSciAffiliations: Rigshospitalet and Copenhagen Academy for Medical Education and Simulation, Copenhagen, DenmarkAmager and Hvidovre Hospital, Hvidovre, DenmarkDisclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L22-0256. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetailsSee AlsoComparison of SARS-CoV-2 Reverse Transcriptase Polymerase Chain Reaction and BinaxNOW Rapid Antigen Tests at a Community Site During an Omicron Surge John Schrom , Carina Marquez , Genay Pilarowski , Chung-Yu Wang , Anthea Mitchell , Robert Puccinelli , Doug Black , Susana Rojas , Salustiano Ribeiro , Valerie Tulier-Laiwa , Jacqueline Martinez , Joselin Payan , Susy Rojas , Diane Jones , Daniel Martinez , Robert Nakamura , Gabriel Chamie , Vivek Jain , Maya Petersen , Joe DeRisi , and Diane Havlir Comparison of SARS-CoV-2 Reverse Transcriptase Polymerase Chain Reaction and BinaxNOW Rapid Antigen Tests at a Community Site During an Omicron Surge John Schrom , Carina Marquez , Maya Petersen , Joe DeRisi , Diane Havlir Metrics Cited byHead-to-Head Comparison of Nasopharyngeal, Oropharyngeal and Nasal Swabs for SARS-CoV-2 Molecular Testing October 2022Volume 175, Issue 10Page: W119KeywordsAntigensCOVID-19Prevention, policy, and public healthReverse transcriptase polymerase chain reaction ePublished: 18 October 2022 Issue Published: October 2022 Copyright & PermissionsCopyright © 2022 by American College of Physicians. 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